Page 103 - Medical Parasitology_ A Textbook ( PDFDrive )

96 10 Nematodes: Roundworms

worm at night. The eggs are sticky and stick to the perianal skin. Pruritus ani causes
scratching and excoriation of the skin around the anus. In female patients, the worms
may cause ectopic migration when they crawl into the vulva and vagina causing
irritation. It may migrate up to the uterus and fallopian tubes. This may cause symp-
toms of cervicitis and chronic salpingitis. The worm is sometimes found in surgi-
cally removed appendix.

Diagnosis
Pinworm infection is suspected from the history of pruritus ani. Diagnosis is made
on the detection of eggs or adult worms.

1. Microscopic examination
Demonstration of eggs or adult female worms using Scotch tape (adhesive
transparent cellophane tape) technique. Specimens are collected from the peri-
anal region during early morning, before going to the toilet or bathing or at night
before going to sleep. Eggs are rarely seen in faeces, so faecal examination is not
useful in diagnosis.
2. Gross examination
Demonstration of adult female worms by Scotch tape technique or on surface
of stool specimen.
3. Histological examination
Identification of adult worms in tissue by demonstration of a pair of cuticular
crests (Fig. 10.10c) and typical D-shaped eggs in the uterus.

Treatment
Pyrantel pamoate (single oral dose), albendazole (single oral dose), or mebendazole
(single oral dose) can be used. Treatment is to be repeated after 2 weeks to kill
worms that might have hatched from eggs ingested following initial treatment. As
pinworm infection is usually transmitted by close contact, it is advisable to treat
household members.

Prevention and Control
1. Hand washing and keeping finger nails short
2. Washing of bed linen
3. Treatment of infected persons and household members

Trichinella spiralis

Distribution
Its infection occurs in pork-eating countries such as Europe and America.

Habitat
The encysted larvae are present in the striated muscles of pig (reservoir host) and
rats. Human is an accidental host.